


To Serenade A Siren

by Gotcha



Category: Undertale (Video Game)
Genre: Aquarist, Aquarist apparently, Aquarium Zoo, Aquariumkeeper?, Aquariums, F/F, F/M, M/M, Reader is like a zookeeper, Reader-Insert, Siren Red, Siren Sans - Freeform, Sirens, aquarium, mermaid Red - Freeform, mermaid au, mermaid sans, reader - Freeform
Language: English
Status: In-Progress
Published: 2021-03-07
Updated: 2021-03-07
Packaged: 2021-03-13 13:47:12
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,234
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29901993
Author URL: https://archiveofourown.org/users/Gotcha/pseuds/Gotcha
Summary: You were on vacation, a much earned vacation - mind you. But your work as a senior aquarist has other plans. Now you have to make sure this... skeleton mermaid is healed before he is released to the wild. However, while he’s here, he better suck up to the guests and show his face to them or so help you, you will jump into his tank and smother his permasmile all over the fifteen inch glass.
Relationships: Sans (Underfell)/Reader, Sans (Underfell)/You, Sans (Undertale)/Reader, Sans (Undertale)/You
Comments: 9
Kudos: 62





	To Serenade A Siren

**Author's Note:**

  * Inspired by [Siren song](https://archiveofourown.org/works/17923892) by [NinaBeena](https://archiveofourown.org/users/NinaBeena/pseuds/NinaBeena). 
  * Inspired by [Scarlet Dreams](https://archiveofourown.org/works/18098531) by [SidonLove](https://archiveofourown.org/users/SidonLove/pseuds/SidonLove). 



> Can somebody help me?
> 
> I’ve read this story before. It’s also an Undertale reader-insert. I can’t seem to remember WHAT THE TITLE WAS OR WHO MADE IT. I really wanna put it up as one of my inspirations for this story.
> 
> So the story goes is that the reader was Sans’ mate (Undertale Sans), but Sans rejected the reader and I’m not sure if I remembered it right that he killed the reader by pushing her off the cliff and she fell to the ocean and eventually died apparently. But that ain’t the end of the story, nay-nay. She was turned into a siren and then met Red (Underfell Sans) who is also a siren. It was a hell of a good story, but I can’t for the life of me remember what its title is or who is its author. I WANNA REREAD IT AND ALSO PUT IT UP AS MY INSPIRATION.
> 
> UPDATE: Hirolu_Wolf helped me and the work is in the inspirations. Omg I really love it
> 
> Another UPDATE: I found the other book that inspired me for this. This is a fanfic of Legend of Zelda: Breath of the Wild Prince Sidon/Reader. I really recommend this story even if its been so long since it’s been updated.

“Pleh pleh pleh.” You smacked your lips and tried to push something out of your mouth with your tongue. Your hand was currently occupied and you felt too lazy to stop holding onto the wood to help yourself get whatever was inside your mouth out of it. The other hand, well you can’t really move it much to your control due to the monstrous parasite attached to it. 

“Are you okay?” A man asked as he used the wooden floaters to pull him closer to you. The two of you bobbed up and down in time with the waves out here in the sea. The only thing not letting the two of you drift away were the wooden floaters which you both have hands on. 

You spat out what you thought might be used dental floss from your mouth. Your countenance scrunched up in disgust from the trash that got caught inside your mouth. Rinsing your mouth with the salty seawater the two of your were wading in. “fine... you shouldn’t be worried about me though. I’m more worried about someone who’s inhaling water more than she’s drinking air.” You said as you started to splash the water that you spat out after rinsing away from the both of you. 

“It was to prove a point.” The man sighed as he then pointedly looked at something on the other side of you. The something you specifically called a monstrous parasite. “Now do you understand why I keep saying that you weren’t ready to reach the floaters on your own?”

“Child endangerment, why not.” You rolled your eyes as the two of you now glanced at your other cousin. You and the man were holding onto the wooden floaters which the fishermen on your island built quite far from the coast. The floaters were used to be a frame of some sorts to hold onto the nets of their fish farms. It wasn’t supposed to be leaned on heavily which was what your other cousin is doing to your arm. She clung to you like an overwhelmed kitten who flung herself in a giant bathtub and she wanted OUT. To be honest, you’re pretty sure she chose to hug your arm which was not next to your cousin who is currently giving her the stink eye. 

“You had water safety training, I doubt her life was at risk.” He scoffed. 

“Way to overrate my skills, Niel.” You sighed. Turning your attention back to the younger cousin. “Are you okay, Riot?”

“I’m tired...” She shivered and tilted her head to lay her cheek on your arm. To your right is Nathaniel, the eldest cousin of your generation. You were the youngest cousin of your generation while Henrietta, Riot for short, is the eldest of the next generation of cousins. Your family tree is complex like that so let’s leave it there for the mean time. 

“You still have to swim your way back to the shore.” You reminded her. She can’t just have you pull her, you won’t let her. You like to swim free, thank you very much. 

“I don’t wannaaaaaa.” She whined like the brat she didn’t know she was. Thirteen years old is already a teen, don’t they usually say that? She can’t pull the bratty little girl card if she’s a teen now. 

“Oh that’s fine.” You shrugged your shoulders, jostling Henrietta just a bit in the water. “Should I call you Nemo from now and eternity?”

“Sharkbait. Hoohaha.” Nathaniel added with a teasing smirk to the little girl. Who shrieked in fear and jumped from holding onto your arm to latching her arms around your neck like a koala bear. 

“Nooo!!” Her saline tears now mixed in with whatever snot and seawater dripping from her face, much to your chagrin. “I thought there weren’t sharks in the area!? Why are we swimming if there are sharks??!!!”

“Calm down!” You choked as she hugged too tight around you windpipe. Patting a hand to her shoulder to somewhat pacify her. “The sea doesn’t need to be seasoned anymore, it’s so salty you can get kidney stones big enough to skip on water surfaces.”

“I’m gonna get kidney stones!!???” She’s so gullible, that you could say the world is ending and she could faint on the spot. Not like you will tell her that as a joke right now, you don’t want to drag her unconscious body back to shore. 

“Look, I’ll give you a couple of minutes to chill out, okay?” Deciding to do just that, you held on to her arms to peel them off of you and guided her hands to touch the wood floaters. 

“Don’t leave me!” Henrietta sniffed and dug her fingernails into your skin before she would let go of you. 

“Don’t fucking TEMPT me.” You growled out in frustration, practically shoving her to the floaters at this point. Patience was a trait which you did not pride yourself on, but nevertheless had it. That didn’t mean you would have a good reign of your temper from time to time. “There are reasons why we herd you and the others closer to the shore because if you swim too far on your own, you will eventually get tired and you might drown from over exhaustion.” Sighing was what you can only do to hint at your frustration. “Oh how the world shall be lonely with one less Riot.”

“One less nuisance.” Nathaniel corrected and you splashed water on his face with a mighty swing of your hand. You gave him a look that hopefully portrayed your disappointment because he wasn’t helping you. 

“I just.. wanted to prove myself... that I am a big girl. I’m old enough to reach this.” She muttered as she pressed her face closer to the forearms that rested on the wood surface.

“It’s not about age, Henrietta. It’s about stamina and body mass which can endure long distances either through land or through water.”

“Well duh, I learned it the hard way!”

“Because you weren’t learning with the amicable way!” Nathaniel shouted and they were both glaring at each other until you all heard something.

It was the sound of a soft horn that could emit from a conch shell when you blow on it. It wasn’t loud and ear shattering, but it was enough to catch attention. It’s a sound that is low yet it resonates in your ears, a sound which travels through longer ranges. The three of you checked first your surroundings in the water. Conch shells were commonly used by native passenger boats that wish to dock at a certain town on the island or when these boats are about leave. If there was a boat that is about to pass by, you needed to know so that you won’t time yourself in such a very dire position that could end up being run over by a boat. 

When the coast was literally clear of any boats, you checked the shoreline. The only other people who bothered to blow a conch shell may be someone from your family. For what reason would they be doing that? It’s because cell reception is horrible in the island since it’s too far from the mainland and completely impossible to erect a cell tower from this distance. People don’t use their cellphones to call each other, they just gather by the plaza and socialize then and there. 

In the days when your grandmother was but a young child, your great grandfather made it a habit to use a conch shell to gather all of his ten children for mealtimes. He had a big set of lungs so he had a booming voice and it was at its best when he blows on the conch shell to the point that it can be heard halfway up the mountain. To be fair, the mountains weren’t that high in the first place, but they’re tall nonetheless.

The sound came from the lone person standing on the old pier made of stone. A man with cargo shorts and no top which showcases his beer belly. You knew that beard on his face and that belly, it was your Uncle Anthony. “Oh, that’s fast.” You hummed as you twirl around in the water so that your body faced the island now.

“Merienda!” Nathaniel hollered, his head whipped to you with an excited grin on his face. “Race you?”

“And what about our resident anchor?” You scowled at him. 

“Let her sink.” He slowly drawled which prompted you to splash water on his face again.

“You better start moving, girl.” You poked your cousin on the cheek and she simply whined yet she moved to start the long swim back to shore. 

Family meals are a whole affair. Servings of the food should be able to at least feed a minimum of 20 people. Three people are usually in the kitchen to handle these menial tasks. One of them is usually the head of the kitchen and chooses what to cook for the day, for this vacation it happened to be the sister of your grandmother. Though you were all family and sharing pretty much the same blood, she didn’t give you much shit. “Don’t handpick the noodles!” She scolded you as you came out of nowhere to pick up a noodle from the plate before it got mixed with the sauce. Her hands were full with one giant serving fork and the plate itself so she couldn’t have stopped you even if she saw you a second earlier. She scolded you, but still let you take the noodle since you already touched it. 

“You haven’t washed your hands.” Grandmama Ja wrinkled her nose as she stared at your hand momentarily before going back to the task of dumping the noodles to mix in with the sauce.

“I just came from swimming, I’m as clean as the water.” You winked and quickly dodged the empty plate as Ja aimed for your head with it. 

“Niel! Take your cousin out. Don’t come back inside until you’re both clean!”

“Yes, ma’aam!” You heard Nathaniel’s voice from behind you. He quickly hooked his arms under your armpits and proceeded to drag you out the backdoor. 

Outside, you saw Henrietta filling up the huge container of water that anyone who just came out of the sea would use to take a bath with. Nathaniel let you go once you reached the public bathing area and Henrietta greeted you with a face full of water. The beginnings of another cousin war, you stole the soap from Nathaniel and kicked Henrietta gently but powerful enough for her to tilt forward, her calves got caught against the lid of the container and she fell into the water. Before she could be fully submerged, she held onto the back of Nathaniel’s shirt which prompted him into falling in as well as on top of her. 

You dodged a shampoo bottle chucked at you before you heard your name being called. The three of you froze in places, Henrietta almost able to teeter off the ledge of the water tub while Nathaniel was twirling a wet rag which was directed at Henrietta’s back. The family house had three balconies which faced the left, right and back sides of the house. Above you, standing on the balcony which overlooked the backyard and also where you were currently messing around, is Rico who had his hands against the railing and looking directly at you. “Your phone was ringing earlier,” Your brother said as he waved the very device he was talking about. “The person was named Superior Alien, I supposed that they were important.

“Mysterious lover?!” Henrietta squealed.

“Long lost relative?” Nathaniel joined in with guessing. “Not like we have a lot of them already.”

“That’s one of the branch directors.” You informed them all, raising an eyebrow in curiosity as to why he was calling you. “He mostly manages newcomers, whether employees or new exhibitions.”

“Yeah that, didn’t know that but I trusted my gut which was saying they were important. I tried answering, but it’s either the network was shitty or his network was shitty.”

“I’ll call him again later. Thanks for telling me!” 

Rico waved a hand and left to enter the house. You turned back to the other two with you and you wanted to steal Nathaniel’s rag to whip Henrietta as her face compels you to do so. “You’re gonna go up the mountain, aren’t ya!? Take me with you!”

“I thought you were tired.” You sighed as you started to scrub the soap bar on your body, with your clothes on mind you.

“Of swimming!” She groaned as if saying the word seriously burdened her. “But I could still hike!”

“Bold words. I’ll make you eat them.” You said absentmindedly and bent down by the waist to scrub your legs.

“Kinky.” She hummed and waggled her eyebrows up and down. That resulted in you whacking her at the back of her knees. Henrietta’s legs buckled right after and she was sent tumbling back into the water container with a huge splash.

You almost got sent into the tub when someone ran past behind you and bumped into you. Nathaniel held onto your arm to help steady you in place and then grumbled to the person that ran, “Be careful next time Chammy.” You turned just a bit to look that it was Nathaniel’s younger brother. 

“Sorry!” He apologized to you, but still rushed to get to the outdoor toilets. There were two stalls and apparently they were occupied since he jiggled both doorknobs and they were both locked.

“Nature calls?” You chuckled as you watched him jump in place.

“Inay is at the bathroom inside and Auntie is pooping in the second floor bathroom. How is it that even the outdoor toilets are unavailable for me?” He whined.

“You’re a boy, Chammy. Just do it in the back.” Nathaniel noted.

“But I don’t want to be cursed by anything!”

“Just ask for permission to whoever lives with us first before you go, we still share the same land.” You rolled your eyes, splashing water over your head with a small bucket.

“I won’t get cursed then?”

“As long as you say the words. You’ll be fine.” You waved a hand to send him off.

“Okay, but if I get cursed, I’m gonna shove rocks under you when you sleep.”

“I’d like to see you try.”

Cell reception is hard to come by in this island. The only place you could get a decent signal for a simple call is if you climb up to the top of the mountains. And climbed you did to the nearest mountaintop. Pathways were carved into the mountain slope for easier access to anyone who dared traverse up. More like desperate enough and you needed to call back the one you dubbed ‘Superior Alien’. 

Your work isn’t demanding, neither are those who you work for or who you work with. The ones who inadvertently demand of you are the ones you handle. It’s not their fault to be demanding, it’s just that they’re in an environment in which they cannot help much of themselves so they have to rely on you. 

Even when you reached the mountain top, you still need to shimmy shammy your way to find signal. So it’s basically you being Rafiki and your phone is baby Simba and you’re showing it to the world. It’s your way of saying ‘Here it is! Come cell reception, accept my phone as your own disciple.’

Once you found a spot where you got at least three bars of signal, you started to tap on your phone. Searching through your recent calls and finding just what you were looking for. You didn’t dare move from your spot, else you lose the already decent reception. Out going international calls are painful because they cost a lot more by the minute and you just wanted to make this quick. And it’s a good thing that the one you were talking to had the same thoughts of these calls. 

“How do you fix a fin which is almost torn apart?” He immediately questioned, bringing out the big guns. Ask first, shoot later. No simple greeting, just straight to the point. The Superior Alien was as preemptive as ever.

“I don’t fucking know? We have a vet for that reason!”

“How do you pacify a shark?” He continued right after you said the last word. 

“Give him food?? Sedate him???? Honestly, sir. On the conscious fact that I may seem insubordinate, that is a stupid question for you to ask me.”

“But you’re our consulting marine biologist since you’re not our on-site curator at the moment!”

“Mr. Gonzales, I am well aware of the amount of senior curators in your location as we speak, how is it that you cannot simply pester them with your questions?”

“Because we’re all out of ideas and I lost at least two of them to this... freak of nature!”

“It’s just a fucking fish, sir.” You said with a sigh, rubbing the pads of your fingertips to massage your nose ridge. 

“No, it’s not!” Superior Alien a.k.a Mr. Gonzales shrieked like a child. “Fishes, no matter what they are, they accept sedatives in certain varieties. This one... we’ve shoved medicines inside its.. jaws enough to put a submarine to sleep. And machines don’t sleep!”

“So what did you do?” It was silent right after you asked. You checked the screen of the phone to make sure you still had signal and you were still on call. It wasn’t your signal acting up and the call was still ongoing so you pressed the phone back to your ear. “Yo, Lemonade??”

“... we put it in a cryogenic pod.”

“ARE YOU FUCKING WITH ME?? YOU PUT A LIVE FISH IN THE CRYOPOD??? I DIDN’T EVEN KNOW THE RESEARCHERS IN OUR AQUARIUM HAVE ONE.” You shouted at the top of your lungs at how absurd their decision was. “The only fish put in freezers are dead and are to be eaten of. And you put a fucking exotic fish in an over glorified freezer?!”

“We couldn’t get close to it without it harming us or harming itself.”

“You have extra hands in your disposal, why can’t—“

“I lost six lives today. One was just an intern. Two of them were your fellow senior aquarists.” Mr. Gonzales’ tone was somber and it honestly made you cool down a lot with that reality. “It chomped the head of Justin and ate it in front of our eyes. No one had a chance to do anything as it mercilessly killed anyone within reach. If Mr. Pritchett didn’t specifically order us to keep it alive and bring it back to full health, I would have had it terminated before it could taste human blood.”

You brushed your free hand across your mouth, covering the lower half of your face. Pressing your palm against your skin to help you soothe yourself with this information. The colleagues you just left behind, some you may not know by name, the ones you’ve made connections with for the betterment of handling your animals. They were gone because of a rampaging shark. 

“Hey, you still there?”

You gulped back the dryness of your throat. Nodding your head blankly as you said, “Yeah... yeah I’m here.”

“I need you to come back.”

Oh those dreaded words.

“You need to take Justin’s place.”

“No.” You said with a shaky voice. Clearing your throat a little, you repeated the word with a little more conviction than the last. 

“I know this all comes as a surprise to you, I know you may have your regressions after what I told you what occurred not too long ago.”

Oh understatement of the day.

“Even if I come back, I shouldn’t just leave my position being with my dolphins.” You argued softly. Taking Justin’s position as the curator for sharks meant you won’t be able to have time with your dolphins. 

“You’re our best bet, please. It’s right up your alley.”

“On what end of my alley did you realize that I’m meant to be with sharks?”

“If you see it then you’ll understand.”

“I can’t just leave my dolphins!”

“Unlike in the shark department which Justin didn’t have the opportunity to find an assistant, you have found not only one but a pair of junior assistants who are willing to take care of your dolphins.” You were silent, trying to take everything into account. Mr. Gonzales obviously knew you were not going to outright accept the proposition. “There’ll be a huge compensation. I can guarantee that. We will squeeze the lemons out of Mr. Pritchett for all those bonuses you can get for leaving early in your vacation and for shifting departments in a short moment’s time.”

“That’s bullying, though..”

“Who the fuck cares?” That startled a laugh out of you. Of course out of all the people, this guy doesn’t care much of the Aquarium Director. “Come on, just... takeover for a while until we can hire new curators that can replace Justin and Hermia.”

“Oh no... the other one was Hermia?”

“I’m afraid so...”

“Once I’m done with this bullshit, once you all find a replacement, I can go back to my dolphins, right?”

“Yes.”

You sighed out and thought for a minute. “I’ll be back tomorrow. Or maybe later? I don’t know, my home is hours ahead from America... I have to go now.”

“Yes! Thank you! I’ll notify Mr. Pritchett.”

“Can I get some pictures though? I can’t see them as of the moment, but once I get stable net, I will check them.”

“I’ll spam you, don’t worry.”

“Thanks. I’ll be going now. Good bye, Leon.”

You sighed as you started your travel back down the mountain. All you could think about is the disappointment of your family to what you’re about to do in a few hours.

The cryostasis pod had a very dark sheen of tint film on the glass, so you couldn’t see the true color of the shark. But when your face is smooching itself allover its glass in fascination, you realized something about it. 

“You said it was a shark!” You screeched in exasperation.

“It is!” Mr. Gonzales argued from ten feet away.

“Sharks have pelts of cool gray. This one is vibrant red. It’s so red he’s like Clifford the Big Red Dog. Nay! He’s Bufford the Big Red Shark!”

“I will release him from cryostasis.” A medical technician announced for you, assuming you were ready to do whatever you needed.

“No!” You shook your head and brought out a hand to signal stop. “Wait! I have to prepare.” You grumbled and went to get back to your bag sitting atop a desk. A water bottle was packed inside the bag and you need to quench your small thirst. Everyone just stands still, seriously waiting for you and what you want to do.

Your eyes stared at the pod and you bit your lip in contemplation. Mermaids are myths, but you being a mythology fanatic since you could understand the words spoken by your great grandparents meant that you somehow know what to do when having an encounter the supernatural. Mermaids enchant people with their song and their voices to lure them deeper into the water and drown them to their deaths. Sirens have the same enchanting effect, however, they lure humans to the point they are lucid enough that they won’t realize they’re being eaten alive. You knew the difference between Mermaids and Sirens, you just have to observe the type of animal they were. Prey types were Mermaids who wish not to shed blood, but still resort to humans’ death. Predator types were Sirens, their diet also consists of humans. 

This one... is a weird one. Mermaids and Sirens have one thing in common and it’s that they’re a hybrid of human and fish (or mammal since there are dolphin and whale types). This one was a hybrid of skeleton and fish. 

“... and what are these preparations you speak off??” A security guard, one of which had annoyed you for quite some time now ever since you stepped foot the shark wing.

“I’m preparing my dignity.” 

“For what exactly??!”

“Because I’m going to serenade a siren.” You cleared your throat and checked your phone which actually had a few dozen messages from just one person, but that can wait.

“Who the fuck said—“

“Listen up here, you uncouth brute.” You growled and shoved your water bottle to the guard’s chest. “Your seed brain can’t even comprehend why there was more than one person that died to this monstrosity. I can bet my entire career that you don’t even know what you’re looking at. So if there are any words which was translated by the brain you pooped out of your ass, then feel free to lay it on the ground where my fucks are located.”

“I know I said this is right up your alley, judging by the fact that you know what to do immediately after you saw it... But why do you need to serenade a siren?” Mr. Gonzales asked what seemed to be the collective question for today. 

“You have to challenge it before it challenges you.”


End file.
